Indentation of nanotwinned fcc metals: Implications for nanotwin stability

Cyclic nano- and microindentation, along with indentation creep, were performed on nanotwinned Cu with two twin structures, and on nanotwinned Ag. The results provide evidence that nanotwinned face-centered cubic (fcc) structures are more stable than their nanocrystalline counterparts. The results are put in the important context of the available body of theoretical study of nanotwinned fcc metals, and in particular in the context of the theoretical forecasts of Kulkarni and Asaro [Kulkarni Y, Asaro RJ. Acta Mater 2009;57:2711]. It is shown, for example, that, as predicted, nanotwinned Ag displays performance comparable, if not superior, to nanotwinned Cu.